Switch assembly for use in oxygen environment



W. T. DOWNS .Fume 17, 169

SWITCH ASSEMBLY FOR USEy IN OXYGEN ENVIRONMENT N Sheet Filed Dec. 5,1966 l/I/ilvsll..

June 17, 1969 W. T. DOWNS 3,451,020

SWITCH ASSEMBLY FOR USE IN OXYGEN-ENVIRONMENT Filed Dec. 5, 196e sheet 2ggg KZ @Vim l m u) I sllllll INVENTOR.

W. T. DOWNS lFume l?, 1969 SWITCH ASSEMBLY FOR USE IN OXYGEN ENVIRONMENTSheet Filed Dec. 5, 1966 INVENTOR.

United States Patent Office 3,451,020 Patented June 17, 1969 U.S. Cl.335-206 16 Claims ABSTRACT OF THE DISCLOSUIE A switch assembly includinga board 'with a plurality of reed switches and a printed circuitassociatedtherewith disposed on a first side of the board. A pottingmaterial is disposed on the first side of the board for surrounding theswitches, the printed circuit and electrical leads extending from theprinted circuit. A plurality of bar magnets are disposed on the secondside of the board where one of the magnets is rotatable to actuate oneof three radially arranged switches on the opposite side of the board.There are two other bar magnets which are movable into position by pushbuttons for actuating other reed switches.

The instant invention relates to an electrical switch assembly which isparticularly adapted for use in inflammable and/ or explosiveenvironments and, more specifically, to an electrical switch includingmeans responsive to a magnetic force for movement from a non-currenttransmitting position to a current transmitting position with pottingmaterial surrounding the means and including magnetic means forselectively moving the means to the current transmitting position.

As will become clear upon a full understanding of the invention, theinvention may be used to advantage in various enviroments where a sparkmay cause combustion or an explosion. However, since the switch assemblyof the instant invention is particularly adaptable for use in a poweractuated hopsital bed which may have an oxygen tent associatedtherewith, it will thus be described.

At present, there are many hospital beds being utilized which includeadjustable components. That is to say, numerous hospital beds have ahead portion which may be adjusted, a seat portion which may beadjusted,\and a foot portion which may be adjusted. Various otherhospital beds include one or more of these adjustable portions as wellas other adjustable components. Normally, the adjustments of the bed areaccomplished by use of an electrically operated motor which serves as adrive means to position a portion or component of the bed. One or moremotors may be utilized, and when one motor is utilized, electricallyoperated clutching devices are frequently utilized. An example of onesuch hopsital bed is set forth in U.S. Patent 3,081,463, which issuedMar. 19, 1963. The hospital bed disclosed in the abovementioned patenthas head, seat and foot portions which may be independently adjusted byactuation of a series of clutches and a single electric motor.

A serious problem associated with such power actuated hospital bedsresults from the disposition of the switching assembly on the bedadjacent a patient when an oxygen tent is being utilized with the bed.There are known instances where a patient in an oxygen tent has createdsufficient static electricity to cause a fire by merely combining hishair. Thus, there is a need for an electrical switch which may beutilized to actuate the motor or motors for adjusting the bed withoutthe possibility of shorting or creating a spark when being used withinan oxygen tent. In the past, this problem has not been satisfactorilysolved. For instance, in many prior art assemblies, the switch forcontrolling the motor which adjusts the bed is disposed outside of theoxygen tent and is, in fact, padlocked to a portion of the bed so thatit cannot be moved within the oxygen tent. Attempts have been made tofabricate switching assemblies utilizing extremely low voltage so thatthere is no possibility of a short occurring while the switch isdisposed within an oxygen atmosphere. Also, attempts have been made toprovide mechanical switches. However, to date no switch which may besatisfactory and safely used within an oxygen tent has been developed.

Accordingly, it is an object and feature of this invention to provide anelectrical switch assembly which may be satisfactorily and safelyutilized in highly combustible or explosive environments, such as withinan oxygen tent of a hospital bed.

In general, these and other objects and features of this invention maybe attained in a switch assembly including one or more switches witheach of the switch having a pair of normally spaced metal stripsdisposed in overlapping relationship and a glass enclosure surroundingthe strips for hermetically sealing the strips. Each of the stripsextends through the glass enclosure and current carrying leads are incontact with the strips exteriorly of the enclosure. A potting materialsurrounds the enclosure and the current carrying leads. There is alsoincluded a magnetic means comprising a permanent bar magnet andactuation means for moving the bar magnet into and out of a positionadjacent the enclosure for moving the strips together so that currentmay be transmitted from one strip to the other. The potting material ispreferably resilient so that in the event the switch is dropped, thepotting material absorbs shocks and prevents breakage. In addition, thepotting material prevents liquids from contacting the switch and theelectrical leads, thus preventing shorts. This is a very importantfeature because switches used in hospital beds are very susceptible tobecoming wet. In a preferred embodiment of the instant invention, aplurality of the switches are associated together in a manner to providea switch assembly which is particularly suited for adjusting the head,seat and foot portions of a hospital bed, as for example the hospitalbed disclosed in the aforementioned patent.

Other objects and attendant advantages of the present invention will bereadily appreciated as the same becomes better understood by referenceto the following detailed description when considered in connection withthe accompanying drawings wherein:

FIGURE 1 is a front elevational view partially broken away of apreferred embodiment of the instant invention;

FIGURE 2 is a rear elevational view partly broken away of the embodimentof the instant invention disclosed in FIGURE 1;

FIGURE 3 is a fragmentary cross-sectional view taken substantially alongline 3 3 of FIGURE 1;

FIGURE 4 is a fragmentary cross-sectional view taken substantially alongline 4-4 of FIGURE l;

FIGURE 5 is a fragmentary cross-sectional view similar to FIGURE 1showing a moved position;

FIGURE 6 is an enlarged fragmentary view of the upper portion as shownin FIGURE l;

FIGURE 7 is a cross-sectional view taken substantially along line 7-*7of FIGURE 6;

FIGURE 8 is a cross-sectional view taken substantially along line 8 8 ofFIGURE 6;

FIGURE 9 is a view similar to FIGURE 6 but showing a moved position;

FIGURE l0 is a plan view of a preferred embodiment of the switchcomponent used in the instant invention;

FIGURE 11 is an enlarged fragmentary cross-sectional view takensubstantially along line 11-11 of FIGURE FIGURE 12 is a perspective viewof the preferred embodiment of the switch assembly disclosed anddescribed herein; and

FIGURE 13 is a schematic view of the circuitry utilized in the preferredembodiment of the invention disclosed and described herein.

Referring now to the drawings, wherein like numerals indicate like orcorresponding parts throughout the several views, a preferred embodimentof the switch assembly of the instant invention is generally shown at10. Referring more particularly to FIGURES 10 and 11, the switchassembly 10 utilizes one 0r more means, generally indicated at 12,responsive to a magnetic force for movement from a non-currenttransmitting position to a current transmitting position, the currenttransmitting position being illustrated in FIGURE l1, and a pottingmaterial 14 surrounding the means 12, and magnetic means, generallyindicated at 16, for selectively moving the means 12 to the currenttransmitting position. More specifically,

the means 12 includes a pair of normally spaced metal strips 18 whichare disposed in overlapping relationship to one another and an enclosurewhich surrounds the strips 18 for hermetically sealing the strips 18.The strips 1'8 extend through the enclosure and include terminals 22.The potting material 14 surrounds the enclosure 20 and the terminals 22.The magnetic means 16 comprises a permanent bar magnet which is movedinto and out of close parallel relationship with the enclosure 20 forselectively moving the strips 18 together so that current may betransmitted therethrough. The enclosure 20` is disposed on one side of aboard 24 and the bar magnet 16 is disposed on the other side of theboard 24. Preferably, the board 24 has a printed circuit thereon, whichwill become more clear hereinafter. The potting material 14 ispreferably resilient to absorb shocks and in addition prevents liquidfrom coming into contact with the terminals 22 or the printed circuits,thus preventing shorts.

The switch assembly 10 is particularly adapted for use with a hospitalbed having one motor for selectively adjusting the head, seat or foot,either up or down. As disclosed in FIGURE 12, there is included ahousing, generally indicated at 26, a selector knob 28, which may bemoved to one of three positions for actuating either the head, seat orfoot, and up and down push buttons 30 and 32. The housing 26 includestwo components which are held together by the screws 25. Once theselector knob 28 is positioned in one of the head, seat or footpositions, one of the push buttons 30 or 32 is pushed into the housingto move the selected portion of the bed either up or down.

As best illustrated in FIGURE 4, the assembly includes a board 24 and aplurality of switches 40, 41, 42, 43, 44, 45 and 46, all of which aredisposed on a first side or face of the board 24. Each of the switches40 through 46 includes a pair of normally spaced metal strips disposedin overlapping relationship with an enclosure surrounding each pair ofstrips in spaced relation to the strips for hermetically sealing thestrips and each pair of strips extends through the associated enclosure.There is also included current carrying means comprising the electricalcable 50, which includes a plurality of leads, and the circuits printedon the first side of the board 24, which are described more specificallyhereinafter. As best illustrated in FIGURES 3 and 4, the pottingmaterial 14 is disposed on the first side of the board 24 and surroundsthe glass enclosures, the leads and the printed circuits. As bestillustrated in FIGURE l, the assembly also includes magnetic means,generally indicated at 16', disposed on the second side of the board 24for selectively moving the strips of each switch together so thatcurrent may flow therethrough. The housing 26 surrounds the potting material 14, the board 24, and the magnetic means 16.

Referring now more particularly to FIGURES 2 and 13, one of the stripsof each of the first and second switches 40 and 41 is connected to afirst lead 52. More specifically, one of the strips of each of theswitches 40 and '41 is connected to the printed circuit 54 which is inturn connected to the lead 52. This first lead 52 is adapted to supply acurrent to the switches 40 and 41. The other strips of each of the firstand second switches 40 and 41 are connected to the respective second andthird leads 56 and 58. Thus, upon actuation of the first switch 40,current may be applied to the second lead 56 and upon actuation of thesecond switch 41, current may be applied to the third lead 58.

In addition, one of the strips of third and fourth switches 42 and 43are connected respectively to a fourth lead 60 by way of the printedcircuit 62. The fourth lead 60 is also adapted to supply a current. Oneof the strips of each of the fifth, sixth and seventh switches 44, 45and 46 is connected to the other strips of the third and fourth switches42 and 43 by way of the printed circuit 64. The other strips of thefifth, sixth and seventh switches 44, 45 and 46 are connectedrespectively to the fifth, sixth and seventh leads 66, 68 and 70respectively, such connections being by way of the printed circuits 72,74 and 76 respectively. Thus, upon actuation of either of the third andfourth switches 42 and 43, current may be supplied to one of the fifth,sixth and seventh leads 66, 68 and 70, depending upon which one of thefifth, sixth and seventh switches 44, 45 and 46 is actuated.

The first switch 40 and the third switch 42 are disposed in side-by-sideparallel relationship. A first permanent bar magnet 78 is moved into andout of close parallel relationship to the rst and third switches 40 and42 to move the respective strips thereof together. The magnet 78 ismoved by a first actuation means which is generally indicated at `80. Inaddition, the second and fourth switches 41 and 43 are also disposed inside-by-side parallel relationship and a second permanent bar magnet 82is moved into and out of close parallel relationship to the second andfourth switches 41 and 43 by a second actuation means, generallyindicated at 84. The bar magnet 82 moves the strips of the second andfourth switches 41 and 43 together when moved into close relationshipthereto by the actuation means 84. Thus, the magnet means 16' includesthe first and second magnets 78 and 82 and the first and secondactuation means and y84.

Each of the first and second actuation means 80 and 84 includes a magnetsupport member 92 which is rotatably attached to the second side of theboard 24 by the pin 94. That is to say, the support members 92 areIdisposed on the board 24 for rotation about a common axis. The firstmagnet 78 is secured to one of the support members 92 and the secondmagnet 82 is secured to the other support member 92. Each of theactuation means 80 and 84 also includes a push button, the push buttonsbeing shown at 30 and 32. Each of the push buttons 30 and 32 is slidablysupported in the housing 26 for movement toward and away from the board24. There is also included a motion transmitting means operativelyinterconnecting each support member 92 and each of the push buttons 30and 32 for rotating the support members 92 upon movement of theassociated push button in a first direction into the housing. When themember 92 of the first actuation means 80 is moved to the positionillustrated in full lines in FIGURE 5, the first bar magnet 78 is in theclose parallel relationship with the first and third switches 40 and 42.Likewise, when the support member 92 of the second actuation means 84 ismoved to the position shown in phantom in FIGURE l, the bar magnet 82 isin the close parallel relationship with the second and fourth switches41 and 43.

It will be noted that the support members 92 include projecting portions96 and one of the support members 92 includes a stop member 98 securedthereto and in the plane of the other support member 92, thus providinga stop means for preventing rotation of either of the support members 92to the central position, i.e., the position illustrated in phantom inFIGURE 1 or the position illustrated in full lines in FIGURE 5, when theother support member 92 is in such a position. There is also included abiasing means comprising the springs 100 which urge each of the supportmembers 92 to rotate away from the positions illust-rated in phantom inFIGURE 1 and in full lines in FIGURE 5.

The motion transmitting means interconnecting the push buttons and therespective support members 92 comprises a spiral surface 102 presentedby each support member 92 and a coacting spiral surface 104 presented byeach push button. The spiral surface 104 of each push button slidesalong the spiral surface 102 of the associated support member 92 torotate `the Iassociated support member 92 toward the central position(i.e., the position illustrated in phantom in FIGURE 1 and the positionillustrated in full lines in FIGURE 5) as the associated push button ismoved into the housing 26. Each button has a cylindrical projection 105which extends through the board 24 and is slidably disposed in a cavity107 in the potting material 14. The projections 105 aid in guiding themovement of the respective buttons 30 and 32.

The fifth, sixth and seventh switches 44, 45 and 46 are disposed onspaced radials extending from a iirst axis 86, the axis 86 beingperpendicular to the board 24. The magnet means 16 also includes a thirdpermanent bar magnet 88 and a third actuation means, generally indicatedat 90. The actuation means 90 moves the -third magnet 88 between rst,second and third positions. More specically, the third magnet 88 is inclose parallel relationship to the fth switch 44 to move the stripsthereof together when in the rst position, which is illustrated inFIGURE 9. The third magnet 88 is in close parallel relationship to thesixth switch 45 to move the strips thereof together when in the secondposition, as illustrated in FIGURES 1 and 6y through 8. The third magnet88 is in close parallel relationship to the seventh switch 46 to movethe strips thereof together when in the third position which is evidentbut not illustrated.

The third lactuation means 90 comprises a rot-ary selector secured tothe second side of the board 24. The selector includes a rotatable shaft106 which extends through the housing 26 for receiving the selector knob28. The shaft 106 is coaxial with the first axis 86 about which theswitches 44, 45 and 46 are radi-ally disposed. A brace 108 supports therotary selector on the board 24. Preferably, the brace 108 and relatedsupport components, such as the screws 110, are made of non-magneticmaterial. A member 112 is attached to the shaft 106 for rotationtherewith. The third magnet 88 is secured to the member 112 with thelongitudinal -axis of the magnet 88 being disposed on a radial of theaxis 86. The rotary selector is preferably of the detent type so thatwhen moved to a particular position a detent, or the like, maintains theswitch in `the selected rotary position. Thus, the shaft 106 isrotatable to move the third magnet 88 from the first position asillustrated in FIGURE 9, to the second position as illustrated inFIGURES l and 6 through 8, to the third position which is notillustrated, and vice versa.

As mentioned herenbefore, the embodiment of the switch assemblyspecically described herein is particularly suitable for use with ahospital bed of the type disclosed in the aforementioned Patent3,081,463. The hospital bed disclosed in Patent 3,081,463 has a headportion which moves up or down, a seat portion which moves up or down,and a foot portion which moves up or down. A single reversible ACcurrent operated motor is utilized in conjunction with three DC poweractuated clutches. A DC current is supplied through the lead 60. The ACcurrent for the motor is supplied through the lead 52. It will be notedthat the tirst and second switches 40 and 41 are larger than theremaining switches. This is because the rst and second switches 40 and41 carry a relatively high AC current to the motor and are, therefore,required to be larger than the remaining switches 42 through 46 whichcarry a relatively lower DC current to the clutches.

The selector knob 28 is in either the head, seat or foot position sothat at all times one of the fth, sixth o1 seventh switches 44, 45 and46 is closed whereby current may pass therethrough. Assuming that theselector switch is in the seat position as illustrated in FIGURE 12, theoperator may push either the up button 30 or the down button 32 to raiseor lower the seat portion of the bed. Assuming that the up button 30 ispressed, the rst bar magnet 78 is moved into close parallel relationshipwith the first and third switches 40 and 42, although the bar magnet 78is on the opposite side of the board 24 from the first and thirdswitches 40 and 42. Thus, the strips in the respective switches 40 and42 are moved together to allow current to pass therethrough. While thebutton 30 is depressed, the projections 96 on the support members 92prevent the down button from being depressed to actuate the second andfourth switches 41 and 43. Once the up button is depressed, AC currentflows from the lead 52 through the rst switch 40 to the lead 56 whichrotates the AC motor in one direction. If the down button is depressed,AC current flows through the switch 41 and to the lead 58 to rotate theAC motor in the opposite direction.

When the up button is depressed, the iirst switch 40 is closed and thefourth switch 42 is closed. The fourth switch 42 is disposed inside-by-side parallel relationship with the switch 40 so that the switch42 is closed momentarily before the switch 40. Likewise, the switch 43is closed momentarily before the switch 44 when the down button 32 ispushed. Thus, the appropriate clutch is actuated momentarily before theAC motor begins to rotate, thus providing a smooth operation.

When the switch 42 is closed and the selector 28 is in the seatposition, DC current passes through the sixth switch 45 and to the lead68 to a clutch which transmits rotary motion from the AC motor to themechanism to raise the seat portion of the bed. When the down button 32is depressed, current passes through the switch 43, and through thesixth switch 45, and to the lead 68 to engage the clutch which transmitsrotary motion from the AC motor to the mechanism connected with the seatportion of the bed to lower the seat portion. In a similar manner, theselector knob 28 may be positioned in either the head or foot positionso that either the head or foot may be raised or lowered by depressingeither the up push button 30 or the down push button 32.

'I'he instant invention, therefore, provides a switching assembly whichis suitable for use in inflammable or explosive environments because ofthe possibility of electrical shorts or sparks occurring is negated.

The invention has been described in an illustrative man- -ner and it isto be understood that the terminology which has been used is intended tobe in the nature of words of description rather than of limitation.

Obviously, many modications and variations of the present invention arepossible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A switch assembly comprising; a. pair of normally spaced metal stripsdisposed in overlapping relationship, an enclosure surrounding saidstrips for hermetically sealing said strips, each of said stripsextending through said enclosure, a board supporting said enclosure on arst side thereof, a printed circuit on said rst side of said board andin electrical contact with said strips, current carrying means incontact with said printed circuit exteriorly of said enclosure, apotting material disposed on said first side of said board andsurrounding said enclosure, said printed circuit and said currentcarrying means, a permanent bar magnet and actuation means for movingsaid magnet into and out of close relationship with said enclosure forselectively moving said strips together, said magnet and said actuationmeans being disposed on the second side of said board, and a housingsurrounding said potting material and said board, said actuation meansincluding a magnet support member rotatably attached to said second sideof said board, said magnet being secured to said support member, a pushbutton slidably supported in said housing for movement toward and awayfrom said board, and motion transmitting means operativelyinterconnecting said support member and said push button for rotatingsaid member to a first position where said magnet is in said closerelationship with said enclosure upon movement of said push button in afirst direction.

2. A switch assembly as set forth in claim 1 wherein said actuationmeans rotates said magnet into and out of said close parallelrelationship to said enclosure.

3. A switch assembly as set forth in claim 2 wherein said enclosure ismade of glass and said potting material is resilient to absorb shocksand prevent breakage of said glass.

4. A switch assembly as set forth in claim 1 wherein said actuationmeans includes a rotary selector secured to said second side of saidboard with a shaft extending through said housing, said rotary selectorhaving a member attached to said shaft for rotation therewith, saidmagnet being secured to said member with the longitudinal axis thereofdisposed on a radial from said shaft, said rotary selector having oneposition in which said magnet is disposed in said close relationshipwith said enclosure.

5. A switch assembly as set forth in claim 1 including biasing meansurging said support member to rotate away from said first position andto urge said push button to move in a direction opposite to said firstdirection.

6. A switch assembly as set forth in claim 5 wherein said motiontransmitting means comprises a spiral surface presented by said supportmember and a coacting spiral surface presented by said push button sothat one surface slides along the other to rotate said support membertoward said first position as said push button is moved in said firstdirection.

7. A switch assembly comprising; a board, first and second groups ofswitches disposed on a first side of said board, each of said groupsincluding a plurality of switches, each of said switches including apair of normally spaced metal strips disposed in overlappingrelationship and an enclosure surrounding said strips in spaced relationthereto for hermetically sealing said strips, said strips extendingthrough said enclosure, a printed circuit on said first side of saidboard and in electrical contact with said strips, current carrying meansin Contact with said printed circuit exteriorly of said enclosures, apotting material disposed on said first side of said board andsurrounding said enclosures, said printed circuit and said currentcarrying means, magnetic means disposed on the second side of said boardfor selectively moving said strips of each pair together so that currentmay ow therethrough, and a housing surrounding said potting material,said board, and said magnetic means, said current carrying meansincluding an electrical cable comprising a number of leads extendingthrough said housing and in electrical contact with said strips of saidswitches through said printed circuit, said first group of said switchesbeing electrically connected by said printed circuit to a first of saidleads which supplies current, each of said first group of switches beingconnected to one of a first plurality of said leads whereby current maybe selectively supplied to any one of said first plurality of leads,said second group of said switches being electrically connected by saidprinted circuit to a second of said leads which supplies current, eachof said second group of switches being connected to one of a secondplurality of said leads whereby current may be selectively supplied toany one of said second plurality of leads, at least one switch of saidfirst group disposed adjacent a switch of said second group whereby saidmagnetic means actuates both switches substantially simultaneously.

S. A switch assembly as set forth in claim 7 wherein said first groupincludes first and second switches, one of said strips of each of thefirst and second switches being connected to said first of said leads,the other strips of each of said first and second switches beingconnected to respective third and fourth leads of said rst plurality ofleads so that upon actuation of said first switch current may be appliedto said third lead and upon actuation of said second switch current maybe applied to said fourth lead.

9. A switch assembly as set forth in claim 8 wherein said second groupincludes third, fourth, fifth, sixth and seventh switches, one of saidstrips of said third and fourth switches being connected to said secondlead, one of said strips of said fifth, sixth and seventh switches beingconnected to the other strips of said third and fourth switches, theother strips of each of said fi-fth, sixth and seventh switches beingconnected respectively to fifth, sixth and seventh leads of said secondplurality of leads so that upon actuation of either of said third andfourth switches current may be supplied to one of said fifth, sixth andseventh leads upon actuation of one of said fth, sixth and seventhswitches.

10. A switch assembly as set forth in claim 9 wherein said first andthird switches are disposed in side-by-side parallel relationship andsaid magnetic means includes a first permanent bar magnet and firstactuation means for moving said first magnet into close parallelrelationship to said first and third switches to move the respectivestrips thereof together, and wherein said second and fourth switches aredisposed in side-by-side parallel relationship and said magnetic meansincludes a second permanent bar magnet and second actuation means formoving said second magnet into close parallel relationship to saidsecond and fourth switches to move the respective strips thereoftogether.

11. A switch assembly as set `forth in claim 10 wherein said fifth,sixth and seventh switches are disposed on spaced radials extending froma first axis which is perpendicular to said board, and said magneticmeans includes a third permanent bar magnet and third actuation means tomove said third magnet between first, second and third positions, saidthird magnet being in close parallel relationship to said fifth switchto move the strips thereof together when in said first position, saidthird magnet being in close parallel relationship to said sixth switchto move the strips thereof together when in said second position, saidthird magnet being in close parallel relationship to said seventh switchto move the strips thereof together when in said third position.

12. A switch assembly as set forth in claim 11 wherein each of saidfirst and second actuation means includes a magnet support memberrotatably attached to said second side of said board, said first magnetbeing secured to the support member of said first actuation means andsaid second magnet being secured to the support member of said secondactuation means, each of said first and second actuation means furtherincludes a push button slidably supported in said housing for movementtoward and away from said board and motion transmitting meansoperatively interconnecting the support member and the push button forrotating the support member to a first position upon movement of thepush button in a first direction into said housing, said first magnetbeing in said close parallel relationship with said first and thirdswitches when said support member of said first actuation means is insaid first position, said second magnet being in said close parallelrelationship to said second and fourth switches when said support memberof said second actuation means is in said first position.

13. A switch assembly as set forth in claim 12 wherein said supportmembers are disposed on said board for rotation about a common axis,said support members including stop means for preventing rotation of oneof said support members to its first position when the other supportmember is in its irst position, and including biasing means urging eachof said support members to rotate away from the respective firstpositions.

14. A switch assembly as set forth in claim 13 wherein said motiontransmitting means comprises a spiral surface presented by each supportmember and a coating spiral surface presented by each push button sothat the spiral surface of each push button slides along the spiralsurface of the associated support member to rotate the associatedsupport member toward its rst position as the push button is moved intosaid housing in said first direction.

15. A switch assembly as set forth in claim 14 wherein said thirdactuation means comprises a rotary selector secured to said second sideof said board with a rotatable shaft extending through said housing andcoaxial with said irst axis, said selector including a member attachedto said shaft ifor rotation therewith, said third magnet being securedto said member with the longitudinal axis thereof disposed on a radialof said first axis, said shaft rbeing rotatable to move said thirdmagnet -between said first, second and third positions thereof.

16. A switch assembly as set forth in claim 15 wherein said enclosure ismade of glass and said potting material is resilient to absorb shocksand prevent breakage of said glass.

References Cited UNITED STATES PATENTS 3,161,742 12/ 1964 Bagno 335-202X 3,260,820 7/ 1966 OBrien 335-153 3,281,734 10/1966y Ansley 335-1523,364,318 1/ 1968- Bulliet.

BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, JR., AssistantExaminer.

U.S. Cl. X.R. ZOO-168; 317-112

